Cummins 4BTA 2A One Ton HiCap

[oldhaven]

I've been driving this for about a year after a 10 year project. Noisy but surprisingly civilized. Full width F250 8 lug front, 14 bolt rear, Ford F350 ZF 5 spd with np 205, Defender/RR coil suspension, 68 mph highway cruise at 1800 rpm. Not sure if it belongs here but it looks like a LR, and I have two more real ones so I qualify. Ron Franklin, Bowdoin, Me.

[o2batsea]

Ron, it looks like...

There's room in there for a 6. Maybe the V10? Maybe have to move the rad to the cab roof for better fit! U GO BOY!

[landi41]

Not sure if it belongs here but it looks like a LR, and I have two more real ones so I qualify. Ron Franklin, Bowdoin, Me.

Oh i'd say you belong allright.........Nice job, no 1/2 measures there with that driveline either.........

[TeriAnn]

I've been driving this for about a year after a 10 year project. 68 mph highway cruise at 1800 rpm

The engine has lots of fans but you are one of the few that seem to have experience with one. A few questions:

1. How much does the engine weigh?

2. What is the engine max cruise RPM? what RPM range is the engine happiest with?

3. What R&P ratio do you have?

What is your low range first gear ratio?

Thanks!

[oldhaven]

Thanks

Hi TeriAnn,
We spoke a bit about this project when I started it long ago, about the time your rig was in its second incarnation (or was it the third?) and it took this long since lots of (expensive) false starts happened along the way. I think I finally got it about right. It resembles the one-ton LR prototypes you can see in Lindsey Porter's book.

Thanks all for the compliments. I am pretty pleased and hope to make a few creature comfort improvements, like sound insulation, but is is well suited to its role as a work truck. I drive it nearly daily to work. I have used it in the woods quite a bit and it is quite literally a stump puller for me. I am not really into rock climbing or gettng lost in a mud pit on purpose. It is pretty light in the rear anyway with the aluminum bed (I can awkwardly pick the bed up by myself) so traction back there could be better. I will need to get a brake proportioner installed as the huge rear drums lock easily unless a light touch is used even though overall weight is pretty well balanced due to the engine position. (HydroBoost brakes with F150 power steering box run off an engine mounted gear driven hydraulic pump)

As for room for a Cummins 6. If a newer radiator panel from a Defender was used that would be quite possible, though this one seems to have all the power (torque) I need The 3.9 4BTA as used in boats can get 250 HP and huge torque. Mine is probably closer to 140, with 325 ft/lbs at 1876, which is 65 mph highway cruise in fifth OD. That is a happy point for the engine, and hills mean nothing. The non-automotive fuel pump works almost as a cruise control to maintain rpm with no pedal input, so I just watch the boost gauge and pyrometer. I hardly ever use first gear in high range as 3.04 second is a good starting gear.

The engine weighs 700 lbs more or less, while the cummins 6 is about 950, so that's another reason to avoid the bigger engine. It may vibrate a bit more, but I don't consider it unreasonable now.

Max comfortable rpm as my fuel pump is set is about 2600. It could turn 2800. I don't need that as I can do 70 with the 33 inch tires at 2020. 100mph is theoretically possible, but you won't see me there testing the theory. Axle ratios are 3.73. Final ratio in fifth high range with .76 OD is 2.83, final ratio in low range with the 5.72 first is 42.67 at which max torque is achieved at 4 mph and even at 2mph the torque is still above 200 ft/lbs. I have idle set at 750 rpm.

As for disadvantages, it does blow a bit of smoke when accelerating too quickly, (great for getting rid of tailgaters), and my dog can hear me coming a ways down the road due to the distinctive Cummins clatter and lets my wife know to expect me.

Ron

[yorker]

what is your average mpg?

[oldhaven]

mileage

I have yet to figure out the interface between the transfer case and the LR speedometer, so I drive by engine rpm for speeds. By watching the engine hour meter, guessing at average miles per hour run and how much and when I fill up the front and rear tanks I know I am getting over 20, but how much....???? If anybody knows of a way to plug two different speedo cable ratios into a black box and come out with correct speed and odometer I would appreciate knowing about it.

Ron

[leafsprung]

ditch the speedo cable and get a norscogg gps speedo

[slorocco]

What did you do with the front springs to fit the full width axles under there? I'm toying with some ideas myself but cant seem to get the full width stuff under there without outboarding the front springs.

[J!m]

Get generic spring perches and weld them on to the new axle tube to align with the series frame. "Outboarding" the series springs does not sound like a good idea to me, and prevents you from ever going back should the need arise.

Also, keeping the springs inboard allows wider tires with no loss in turning circle. In fact, I'd almost bet your turning circle would be much improved over the stock series...

[slorocco]

Get generic spring perches and weld them on to the new axle tube to align with the series frame. ...

Gee, why didn't I think of that . All kidding aside, I'd have done that if it were feasible, but it cannot be done with full width axles. You'd have to weld one of the spring perches right on top of the pumpkin. Your two choices are to either shorten the axle width or outboard the springs.

[J!m]

Yes, shortening one side of the axle to get the diff where it should be I thought was obvious, but perhaps not...

Fo those who don't know, you have to have all your drive line angles correct (diff input parallel to t-case output [most important] and side angle as close to zero as possible under the weight of the truck at rest [slightly less important]). If the transfer case output is outside the frame rail, then the pumpkin needs to be outside the frame rail (and your spring perch needs to be ON the diff, like the stock series nearly is). If the transfer box output is within the frame rails, the diff needs to be within the frame rails.

You want no angle to the side if it can be avoided- the drive shaft parallel to the frame rail (and it obviously can be in this case, since you are making it up custom), so set it correctly before you weld it, or have an axle made up the correct width with the diff in the correct place. There are several companies who do this sort of work, and this is what we refer to as "the right way" to set up custom rigs, if you simply MUST change out the axles. I'd suggest a set of Ford 9 inch front and rear, so you have the removable third member like a stock series truck for quick repairs (although they don't break).

Now the stories come pouring in of how "it's been XXX years since I did mine and it's fine" well, take the chance then. Meanwhile, look under any factory car or truck and see how the side angle is as close to zero as possible... Do you think there may be a reason for this? Hmmm....

[slorocco]

Not looking to get into a discussion of what's obvious or not. OldHaven stated he was using full width axles, not narrowed axles, hence my question to OldHaven on what he did with the springs.

[oldhaven]

front end revealed

changed to coils and redid the mounts inboard lined up with standard 110 upper mounts

[oldhaven]

more suspension pictures

No mysteries, just a lot of welding and fitting